Guy, You may find the idle screw is there, nicely seized into the alloy body, with the slotted screw head sheared off. The business end of the screw will be felt in the throttle slide position, locating the vertical slot in the throttle slide. You may be lucky, but now the throttle slide is no longer easily adjustable more likely this is why the carb was discarded as backyard repairs are impossible.
Swarfy.